The range of the basic d.c. voltmeter can be extended by using number of multipliers and a selector switch. Such a meter is called multirange voltmeter and is shown in the Fig. 1.

Fig.1 multirange voltmeter |

The R

_{1}, R_{2}, R_{3}and R_{4}are the four series multipliers. When connected in series with the meter, they can give four different voltage ranges as V_{1}, V_{2}, V_{3 }and V_{4}. The selector switch S is multiposition switch by which the required multiplier can be selected in the circuit.
The mathematical analysis of basic d.c. voltmeter is equally applicable for such multirange voltmeter. Thus,

__1.1 Practical Multirange Voltmeter__

In this arrangement, the multipliers are connected in series string. The connections are brought out from the junctions of the resistances. The selector switch is used to select the required voltage range.

When the switch S is at position V

_{1}, R_{1 }+ R_{2 }+ R_{3 }+ R_{4}acts as a multiplier resistance. While when the switch S is at position V_{4 }then the resistance R_{4 }only acts as multiplier resistance. The V_{4}is the lowest voltage range while V_{1 }is the maximum voltage range.
The multiplier resistances can be calculated as :

In position V

In position V

In position V

In position V

_{4}, the multiplier is R_{4 }only. The total resistance of the circuit is say R_{T }.In position V

_{3}, the multiplier is R_{3 }+ R_{4}.In position V

_{2}, the multiplier is R_{2 }+ R_{3 }+ R_{4}.In position V

_{1}, the multiplier is R_{1 }+ R_{2 }+ R_{3 }+ R_{4}.
Using equations (1), (2), (3) and (4) multipliers can be designed. The advantage of this arrangement is that the multiplier except R

_{4 }have standard resistance values and can be obtained commercially on precision tolerances. The first resistance i.e. R_{4 }only is the resistance having special value and must be manufactured specially to meet the circuit requirements.
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